CO2 emissions could mean more dangerous space junk

Kate Taylor, 12th November 2012

Rising levels of carbon dioxide in the atmosphere are leaking out to the edge of space and interfering with satellites, new research shows.

The increase in CO2 is expected to gradually result in a cooler, more contracted upper atmosphere - which means less drag on satellites and a possible increase in space junk.

The American/Canadian team studied eight years of CO2 measurements made by the Atmospheric Chemistry Experiment (ACE), a scientific satellite mission funded primarily by the Canadian Space Agency.

While CO2 traps heat in the troposphere, it works as a coolant at higher altitudes, where it's not dense enough to recapture the heat that it emits.

"In the upper atmosphere, thermal energy is transferred via collisions from other atmospheric constituents to CO2, which then emits the energy as heat that escapes to outer space," says Dr John Emmert, from the Naval Research Laboratory's Space Science Division.

And the cooling caused by the increasing CO2 results in a more contracted thermosphere - where many satellites, including the International Space Station, operate. This will reduce atmospheric drag on satellites.

And, say the scientists, it could have dangerous consequences for orbital debris, by slowing the rate at which debris burns up in the atmosphere.

The problem appears to be much worse than expected. The scientists estimate that the concentration of carbon near 100 km altitude is increasing at a rate of 23.5 ± 6.3 parts per million per decade - about 10 ppm/decade faster than predicted by upper atmospheric model simulations.

The authors speculate that this might be because of changes in upper atmospheric circulation and mixing.